Epilepsy: This is often the first consideration for new onset seizures, as it is a common condition characterized by recurrent seizures due to abnormal electrical activity in the brain. The likelihood of epilepsy increases with factors such as family history, previous head trauma, or the presence of other neurological conditions.

Stroke or Transient Ischemic Attack (TIA): Seizures can be a presenting symptom of a stroke or TIA, especially in older adults. The mechanism involves either ischemia or hemorrhage affecting areas of the brain that can provoke seizure activity.
Traumatic Brain Injury: Head trauma can cause seizures, either immediately after the injury or as a late complication. The severity and location of the injury influence the risk of developing seizures.
Infections (Meningitis, Encephalitis): Central nervous system infections can lead to seizures due to inflammation and disruption of normal brain function. The type of infection and the patient's immune status play roles in determining the risk.
Metabolic Disorders: Conditions such as hypoglycemia, hyponatremia, and hypernatremia can precipitate seizures in susceptible individuals. The mechanism often involves alterations in the balance of electrolytes and fluids that affect neuronal function.

Subarachnoid Hemorrhage: Although less common, a subarachnoid hemorrhage can present with a seizure as the initial symptom. Missing this diagnosis can be catastrophic due to the high risk of rebleeding and the need for urgent intervention.
Brain Tumors: Seizures can be the first symptom of a brain tumor, particularly those located in the frontal or temporal lobes. Early diagnosis is crucial for treatment and prognosis.
Vasculitis: Inflammatory diseases affecting the blood vessels of the brain, such as central nervous system vasculitis, can cause seizures among other neurological symptoms. Prompt recognition and treatment are essential to prevent further brain damage.

Autoimmune Encephalitis: A group of conditions characterized by an immune-mediated attack on the brain, leading to inflammation and seizures. These are rare but important to consider due to their potential for treatment with immunotherapy.
Mitochondrial Disorders: Genetic conditions affecting the mitochondria, such as MELAS syndrome, can present with seizures as part of a broader spectrum of neurological and systemic symptoms.
Hashimoto's Encephalopathy: A rare condition associated with Hashimoto's thyroiditis, characterized by seizures, altered mental status, and other neurological symptoms, which improves with corticosteroid treatment.